About recent studies of nutrients in organic produce, McGee concludes: "Reliable information is still pretty sparse." His discussion of organics also includes an interview with Arthur R. Grossman of the Carnegie Institution for Science, a plant scientist. He writes:
It’s likely that there will never be a clear winner in the conventional versus organic battle if they are judged strictly by comparing their nutrient scorecards. But Dr. Grossman suggested that organic farming may have a more general nutritional advantage over a system that relies on agricultural chemicals.
“I think it’s likely that plants grown with minimal intervention by the farmer are chemically more complex,” ... “The biochemical machinery in plants is incredibly prolific,” Dr. Grossman said. “They can make hundreds of relatives of beta carotene alone. I’m sure we haven’t identified all the beneficial chemicals in plants. And diversity in the molecules we consume may be beneficial in itself.”
As for yak cheese, which has "higher levels of the essential omega-3 fatty acids that are found in fish and plants" -- he points out that as with the higher omega-3s in grass-fed beef, the total amounts are not actually very high. If you really want omega-3s you should eat fish, walnuts, greens, or other sources that are actually high. His conclusion is that taste should be your guide. I guess this isn't entirely different from Michael Pollan.